The invention relates to a device which comprises a transformer for magnetizing the surface of material of high magnetic resistance.
According to prior art there are known such devices for materials of low magnetic resistance for which however an iron yoke is used as conductor of the magnetic flux. Thereby the strength of the magnetic fields is limited to 1,6.times.10.sup.6 A/m. This value can be raised by using the stray flux of the field inducing coil.